Capsules enclosing various medicines, food, favorite item or the like are widely employed, because one takes capsules easily. In the capsules, seamless capsule are generally used for encapsulating liquid content, because of high productivity. An example of such seamless capsules includes seamless capsules for favorite item or oral care.
In the seamless capsule, a capsule shell has function of a container of a capsule content solution. The capsule shell, accordingly, has strength enough to keep maintaining capsule content solution, when producing seamless capsules. On the other hand, seamless capsules enclosing favorite item or oral care material are desired to smoothly and easily dissolve in the oral cavity, when one takes in them. In the case where capsule shell does not dissolve easily in the oral cavity, the capsule shell remains in the oral cavity and the remaining brings unpleasant feeling like eating rubber.
Accordingly, seamless capsules should have enough strength when producing them and should easily dissolve in the oral cavity when one takes them, which are to be inconsistent properties. It, however, has been difficult that these properties are consistent to a high degree.
JP 2006-512944 A (Patent Literature 1) discloses a spherical capsule comprising a liquid core and a seamless solid shell enclosing the liquid core, wherein the capsule has a diameter of 4 to 8 mm, has a shell thickness of 20 to 200 μm and a ratio of shell thickness and capsule diameter of 0.004 to 0.04, the shell contains a gelatin of 70 to 90% by mass and a plasticizer of 10 to 30% by mass based on a solid content of the shell and the core contains a flavoring agent of 1 to 100% by mass based on a total amount of the core (claim 1). The shell of the spherical capsule is prepared by using a gelatin having a bloom value of at least 200, preferably 240 to 300 (claim 4 of Patent Literature 1). When a gelatin having such a high bloom as disclosed in Patent Literature 1 is employed for producing a capsule, it has been found that the capsule shell does not have sufficient solubility in the oral cavity.
JP H10-512141 A (Patent Literature 2) discloses a method for forming a micro-capsulated food or flavor capsule comprising providing food or flavor particles to be encapsulated; forming a mixture of hot-water fish gelatin and the above-mentioned food or flavor particles in aqueous medium; and micro-encapsulating the particles in the gelatin by a composite coacervation method at an elevated temperature to form a micro-capsulated capsule (claim 1). In this method, the fish gelatin preferably has a bloom value of about 150 to 300, preferably a bloom value of about 250 to 300 (claims 4 and 5). Patent Literature 2 also employs gelatin having high bloom values. The micro-capsule of Patent Literature 2 is obtained by composite coacervation method which is absolutely different from the process of the present invention.